In a typical impeller pump—such as the Gould Model 3196 series of pumps produced by Gould's Pump, Inc., of Seneca Falls, N.Y.—a bearing housing/thrust housing and a bearing frame are two separate items attached to one another in spaced apart relation so as to have a desired spacing. The spacing in some such pumps determines the clearance between the impeller and a housing of the pump. The Gould Model 3196 (and also Model 3175 and 3180) are open impeller pumps, and include a system for adjusting the spacing between the thrust housing and bearing frame—and so the impeller clearance—that has now been in common use for over 30 years. A precise setting of impeller clearance is required to maintain pump efficiency.
The impeller clearance adjustment system used in these pumps is shown in FIG. 1 as including a plurality of evenly distributed jack bolts 14 and corresponding lock nuts 15, and also a plurality of evenly distributed locking bolts 16. The system of jack bolts 14 with lock nuts 15 and locking bolts 16 allows adjusting a spacing 10 between a thrust housing 11 and a frame 12 and so adjusting the clearance of an impeller (not shown) and a suction housing (also not shown) without disassembling the pump. Typically three evenly distributed jack bolts 14—distributed 120 degrees apart—are used, each having a lock nut 15 to fix the minimum separation 10 between the thrust housing 11 and the frame 12, and typically three locking bolts 16 are used—also distributed 120 degrees apart and offset by 60 degrees from the jack bolts—to hold the thrust housing to the frame. The locking bolts 16 fit through a clearance hole in a flange of the thrust housing and thread into the bearing frame. The jack bolts are threaded into the thrust housing flange and abut against the end of the bearing frame. The lock nuts are located between the head of the jack bolt and the thrust housing flange and are used to prevent the jack bolts from loosening during normal operation.
Some other adjusting arrangements involve shims between the thrust housing flange and the bearing frame. Such shim arrangements require that the pump be disassembled in order to adjust impeller clearance.
In addition, U.S. Pat. No. 5,951,244 to Knight, and also U.S. Pat. No. 6,368,053 also to Knight, describe an impeller clearance adjustment system that uses a plurality of pairs of adjustment bolts and mating attachment bolts to provide a desired spacing between thrust or bearing housing and a bearing frame (and so to provide impeller clearance adjustment). Both the thrust housing and the frame have evenly spaced apart pair-wise registerable threaded openings. A threaded adjustment bolt is threaded through an opening of the thrust housing and abuts the frame. The end of each adjustment bolt is squared and the cross section is greater than the cross section of each opening on the frame so that the adjusting bolt does not, and cannot, enter the opening of the frame. The adjustment bolt is dimensioned so that when each is fully inserted into its respective opening in the thrust housing, the impeller clearance is at the greatest desired distance. The attachment bolt is then passed through each aligned opening pair to hold the thrust housing to the frame. The '053 patent additionally describes a twinsert threadably installed in the threaded openings of the frame and also describes locking bolts each being threaded not into the frame itself, but instead into a twinsert (after being passed through a bore opening of a respective adjustment bolt). The holes in the flange of the thrust housing must be a sufficient size to accommodate relatively large diameter adjustment bolts so as to be able to have attachment bolts of sufficient diameter to provide reasonable strength. Since in some pumps the flange of the thrust housing is relatively small, such a design can be problematic.
It would therefore be advantageous to have an impeller clearance adjustment system simpler than the older above described system using both jack bolts and locking bolts, but also one able to provide a stronger attachment of the thrust housing to the frame, especially in case of a relatively small flange on the thrust housing.